A wide range of methods is used for preserving food products. Among these methods are the use of antimicrobial preservatives, e.g. chemicals such as nitrate, sulphur dioxide, benzoic acid, and proteins such as nisin and pediocin. Another method is the addition of an antioxidant such as ascorbic acid, citric acid and tocopherols. Antioxidants prevent oxidation of foods, which would otherwise result in rancidity and discoloration.
EP 0 092 183 B1 discloses a method for preservation of food by providing a culture in the food containing lactose, which generates a bacterial spoilage inhibitory substance.
WO 01/52668 discloses porphyrin-containing lactic acid bacteria and their use for reducing oxygen content in a food product.
Oxygen is a major quality-deteriorating factor with respect to many food products. Oxygen may cause growth of molds and development of rancid off-flavors, which subsequently reduce the quality and shelf life of many food products. It is therefore desirable to reduce the oxygen content in the air having contact with the food product within the packaging. Packaging in modified atmospheres with low residual oxygen has been introduced in order to reduce the quality changes associated with the presence of oxygen.
Presently the residual oxygen level in packaged foods may be reduced by means of the following approaches:                Repeating vacuum and gas flushing cycles to reduce the residual oxygen content. This method is expensive both with respect to amounts of gas used and time used for the gas flushing cycles. Hence, significant increases in packaging costs result.        Use of a chemical oxygen absorber. The present systems utilize one or more of the following concepts: iron powder oxidation, ascorbic acid oxidation, photosensitive dye oxidation, enzymatic oxidation (e.g. glucose oxidase and alcohol oxidase), unsaturated fatty acids (e.g. oleic acid or linolenic acid), or immobilized yeast on a solid material (Vermeiren et al., 1999, 2003). Most of the currently commercially available chemical oxygen absorbers are based on iron powder oxidation. Additionally, enzymatic removal of oxygen has been proposed as a promising technique (Vermeiren at al., 1999, 2003). The oxygen absorbing materials are incorporated into labels, sachets, or into the packaging material. The disadvantages of these systems are that the absorber efficiency is often low and the time used before the system is activated is unacceptably long. Furthermore, legislative aspects in relation to food products in some cases hinder the use of these systems.        
Food products packaged in vacuum or with a modified atmosphere are susceptible to packaging defects, and oxygen enters the packaging on opening of the package during use. Furthermore, obtaining low residual oxygen content in the packaging process is time-consuming and costly.
Thus, there is a need within the food industry to find alternative or supplementary ways of reducing the residual oxygen content in packaged foods. Such alternative ways of reducing residual oxygen content must comply with food regulatory legislation as well as with consumer preferences.